From pharmacy records, the authors identified 17 consecutive patients who were treated with carbamazepine and valproate simultaneously. Twelve patients were diagnosed with bipolar disorder, manic or mixed types; four patients received a diagnosis of schizoaffective disorder, manic type; and one had major depression and posttraumatic stress disorder. All 12 bipolar patients had a moderate to marked response to the combination drug treatment, whereas all 4 schizoaffective patients failed to respond. Only two patients had minor side effects. The authors conclude that the combination of valproate and carbamazepine is usually well tolerated and that it can be effective in bipolar patients who have previously failed to respond to anticonvulsant monotherapy.